1. Field of the Invention
This invention relates to III-nitride electronic and optoelectronic devices, and specifically to III-nitride electronic and optoelectronic device structures having a diffusion barrier of high-Al content AlxGayN, wherein x+y=1, and x≧0.50, and to methods of making same. The high-Al content AlxGayN layer permits electronic and optoelectronic devices to be manufactured that are uncompromised by migration or diffusion of dopant species (e.g., magnesium, silicon, etc.) into the active device region, during the high temperature fabrication steps involving in the manufacture of such electronic and optoelectronic devices, including epitaxial growth and device fabrication.
2. Description of the Related Art
In the manufacture of III-nitride optoelectronic devices, commonly employed dopants such as silicon and magnesium readily migrate or diffuse into active regions of the device structure during high temperature processing conditions such as metalorganic chemical vapor deposition (MOCVD) and post-deposition fabrication operations. Such transport of the dopant species into the active region is severely detrimental to the ultimate performance and efficiency of the III-nitride optoelectronic device.
Specifically, the transport of dopant species into the active region of the optoelectronic device will reduce the luminous efficiency of the device due to formation of non-radiative centers, as well as radiative centers with undesirable wavelength characteristics (i.e., deviations from the desired emission wavelength), and the development of micro-morphological defects, which in turn substantially reduce the efficiency of the product device.
Further, such transport of dopant species into the active region, and the defects that resultantly develop in the device, lead to shortened product life, as a consequence of excessive heat generation during operation, attributable to the presence of dopant contamination of the active region.
These problems associated with dopant transport into the active region of III-nitride optoelectronic devices during their fabrication has motivated study and efforts to modify the optoelectronic device architecture. See, for example, Chang, Ying-Lan, et al., “Study of Mg Diffusion During Metalorganic Chemical Vapor Deposition of GaN and AlGaN,” Applied Physics Letters, Vol. 74, No. 5, pp. 688-690: Japanese Patent Publication 2001-36196, published Feb. 9, 2001; and Japanese Patent Publication 2001-77480, published Mar. 23, 2001. The disclosures of these various references are hereby incorporated herein by reference, in their respective entireties.
Despite such prior study and attempts to overcome problems associated with migration and diffusion of dopant species into active areas of the optoelectronic device, the art is still in need of an effective solution to such problem. Such solution desirably is readily implementable in the manufacturing process of the III-nitride optoelectronic device, highly effective in avoiding migratory or diffusional contamination of the active region of the optoelectronic device structure, and cost-effective.